Oncologic outcomes, prognostic factor analysis and therapeutic algorithm evaluation of head and neck mucosal melanomas in France.

BACKGROUND: Head and neck mucosal melanoma (HNMM) is aggressive and rare, with a poor prognosis because of its high metastatic potential. The two main subtypes are sinonasal (sinonasal mucosal melanoma [SNMM]) and oral cavity (oral cavity mucosal melanoma [OCMM]). Consensual therapeutic guidelines considering the primary tumour site and tumour-node-metastasis (TNM) stage are not well established.

MATERIAL & METHODS: Patients with HNMM from the prospective national French Rare Head and Neck Cancer Expert Network database between 2000 and 2017 were included. Clinical characteristics, treatment modalities, outcomes and prognostic factors were analysed.

RESULTS: In total, 314 patients were included. The 5-year overall survival (OS) and progression-free survival (PFS) rates were 49.4% and 24.7%, respectively, in the surgery group; no long-term survivors were observed when surgery was not feasible. Moreover, even after surgery, a high recurrence rate was reported with a median PFS of 22 months. In multivariate analysis, Union for International Cancer Control (UICC) stage and tumour site correlated with PFS and OS. Postoperative radiotherapy (PORT) improved the PFS but not OS in patients with small (T3) SNMM and OCMM tumours. Nodal involvement was more frequent in patients with OCMM (p < 10-4), although, as in SNMM, it was not a significant prognostic predictor.

CONCLUSION: Even early HNMM was associated with poor oncologic outcomes due to distant metastases despite surgical resection with clear margins. Lymph node metastases had no impact on the prognosis, suggesting treatment de-escalation in cervical node management. PORT might be useful for local control.